DescriptionMannophryne olmonae is a rather small frog with a maximum snout-vent-length for males of 21.0 mm ± 2.4 mm and 21.6 mm ± 2.2 mm for females (Alemu et al. 2007). The snout is blunt, looks slightly rounded when viewed dorsally, and sloping when viewed laterally. The canthus rostralis is fairly distinct, rounded, and slightly concave. The loreal region is relatively straight. The nostrils are closer to the tip of the snout than they are to the eyes. The diameter of the eye is greater than the distance between the eye and the nostril. The length of distinct tympanum is about twice the diameter of the eye but partly covered by a poorly developed supratympanic fold. Tubercles are found on the sides, back, and upper surfaces of the legs. Tubercles are also found on the abdomen of the ventral and are absent on the ventral side of the chin, which is smooth. On the dorsal side, a mid-dorsal ridge beginning between the eyes extends to the posterior portion of the body (Hardy 1983).

The general shape of a Mannophryne olmonae tadpole is oval and depressed. The body width is 8.0 mm and the tail (24.5 mm) is longer than the body length (10.8 mm), making a total length of 35.3 mm. The eyes are positioned dorsally on the tadpole with an orbital diameter of 1.4 mm and an inter-orbital distance of 3.9 mm. The distance from the tip of the snout to the eye is 3.2 mm. The nares of the tadpole are positioned anteriolaterally, are closer to the tip of the snout than the eyes, and are circular. The spiracle is sinistral and the overall shape of the tail is relatively pointed and ends in a slightly rounded tip (Lehtinen and Hailey 2008).

The genus Mannophryne contains thirteen species. Only two of the thirteen species are found in the Republic of Trinidad and Tobago while the remaining eleven are found in Venezuela (Lehtinen and Hailey 2008). The two species found in the Republic of Trinidad and Tobago are Mannophryne olmonae, found on the island of Tobago, and Mannophryne trinitatis, found on the island of Trinidad. These two species are similar but can be differentiated by toe webbing, voice, outlines of the facemask, and the number of tadpoles transported by males (Hardy 1983).

In life, the dorsum of Mannophryne olmonae is light brown. Outlines of a facemask are formed by a canthal streak and a dark interorbital triangle. A distinct green-brown “X” on the back of the frog connects to the interorbital triangle by two dark, thin, oblique lines. There is also a dark inverted “V” on the posterior portion of the dorsum. A light brown dorsolateral stripe is fringed by grey-colored extensions of the facemask and a yellow oblique lateral stripe is crossed with irregular bands of grey. The upper surfaces of the legs are light brown with a dark narrow band crossing the mid-point of both the femur and tibia. There is also a second, less distinct but broader band on the femur. On the ventral side, there is a well-defined dark band that crosses the pectoral region and two patches of dark yellow just below this pectoral crossband. The chin and lateral portions of the abdomen are also bright yellow. In recently collected specimens of Mannophryne olmonae, yellow pigment was only visible on the chin and pectoral region of the ventral side at the time of collection. After some time in captivity, the yellow ventral pigment tended to spread over the entire abdomen. In preservative, the pectoral crossband is lighter. The yellow pigment on the ventral side is faded and the ventral side is white except for the lightened pectoral band. The dorsolateral stripe is pale but much more defined than in life. The oblique lateral stripes have dispersed patches of a brownish pigment and the upper and lower jaws are stippled with brown (Hardy 1983).

Coloration of a Mannophryne olmonae tadpole is overall dark brown with pigmentation being especially dark on the lateral and dorsal surfaces. The tail also contains dark pigmentation that forms densely spotted clusters on the fins and musculature. On the ventral surface of the body, there is less pigmentation resulting in the intestinal coil being easily visible (Lehtinen and Hailey 2008).

Males and females of Mannophryne olmonae display little to no sexual size dimorphism but there is quite a bit of variation between individuals in regards to pigmentation and skin patterns. Most are pigmented brown on the dorsal side but some can be grey or greyish-green; and the dorsal pattern previously described in detail tends to be obscure or even lacking in most individuals. The oblique lateral stripe is variable and sometimes only visible as a series of white dashes or spots. In males, the chin, abdomen, arms, and legs of the ventral side are finely stippled with black. In medium-sized females, the abdomen is spotless in contrast to larger females who tend to have chromatophores scattered on the anterior half of the abdomen and legs of the ventral side. The loreal region is usually a whitish color and marked with dark stippling but can also be predominantly dark in some individuals. Hind legs usually have defined bands across the femur and tibia but in some individuals, more widespread, dark pigmentation blots out these bands (Hardy 1983).

Mannophryne olmonae is endemic to the island of Tobago in the West Indies. It can be found in mountainous areas of the island (Hardy 1983). Adult frogs are normally found near streams in forested areas usually about 2.0 meters from the water edges (Alemu et al. 2007). Tadpoles of M. olmonae are typically found in small pools of water formed from crevices of rocky substrate. Although these pools are usually near a stream, tadpoles are never found within the streams, only in the rocky pools. Pools are generally less than one meter in length and less than 10 cm in depth. Within each pool of water, one can usually find the pool to be densely populated ranging from 50 or more individuals per pool (Lehtinen and Hailey 2008).

Life History, Abundance, Activity, and Special BehaviorsMannophryne olmonae is a diurnal frog typically found within 2 - 10 m of the water’s edge. The only adult frogs not found near the edge are adult calling males. Often times vocalizations of calling males are heard further away from the edge of rivers or streams (Alemu et al. 2007). Male vocalizations for mating purposes consist of short notes that are repeated rapidly with only a single pulse per note. Pulse duration and the interval between notes are long and the change in frequency from the beginning to end of each pulse varies over a large range (Lehtinen et al. 2010).

Adult males display tadpole transport. When the eggs have hatched, tadpoles are transported in large numbers on the backs of adult males. Tadpoles are carried and deposited in small rock pools where there are fewer predators. The large size of tadpole populations in pools suggests there are many depositions by multiple males. Based on food contents available in rocky pools and analysis of tadpole gut contents, tadpoles are thought to most likely be detrivores (Lehtinen and Hailey 2008).

Trends and Threats

In 2006, Mannophryne olmonae was listed as “Critically Endangered” in the IUCN Red List as because of a more than 80 percent population decline over the previous three years, a markedly fragmented distribution, and an ongoing decline in adult individuals (Alemu et al. 2007). Chytridiomycosis, an infectious disease caused by the chytrid fungus Batrachochytrium dendrobatidis, has also been suggested to be a cause of population decline. This disease has now been described to be endemic to the species and not epidemic, meaning the species seems to have avoided the threat of extinction by this emerging disease (Alemu et al. 2008). As a result of continuing population declines, efforts to conserve M. olmonae and other herpetofauna are becoming increasingly important in the Republic of Trinidad and Tobago. Designated Environmentally Sensitive Areas (ESAs) have been created to legally protect species within set boundaries, but additional protection is still needed. The regions of northeast Tobago and the southwest peninsula of Trinidad are also important regions that contribute to amphibian diversity and would therefore also greatly benefit from established ESAs (Hailey and Cazabon-Mannaette 2010).

Possible reasons for amphibian decline

General habitat alteration and lossHabitat fragmentationDisease

Comments

The species authority is: Hardy (1983). ''A new frog of the genus Colostethus from the island of Tobago, West Indies (Anura: Dendrobatidae).'' Bulletin Maryland Herpetological Society, 19(2), 47-57.

The species epithet, olmonae, was given in honor of Janet Olmon, who was a former member of The Virginia Institute of Marine Science (Hardy 1983).

Recent analyses of DNA sequences have led to the current classification of this species in the genus Mannophryne. DNA sequences for five mitochondrial loci and six nuclear loci have been used to improve classification of several species, including M. olmonae. The identification of 174 phenotypic characters for adult and larval morphology, alkaloid secretions, and behavior were also used in addition to DNA analyses to improve classifications. All species sampled in the study were classified into two clades based on toxicity: family Aromobatidae and family Dendrobatidae. Aromobatidae consists of nontoxic species while Dendrobatidae consists of toxic species. Mannophryne olmonae is a member of Aromobatidae in which there are three subfamilies: Anomaloglossinae, Aromobatinae, and Allobatinae. M. olmonae is classified in the subfamily Aromobatinae. All species in this subfamily have a dermal collar, males with an abdomen color that is evenly stippled, a pale oblique lateral stripe and dorsolateral stripe present, toe webbing, and the absence of lipophilic alkaloids (Grant et al. 2006). In 2008, partial sequences of cytochrome oxidase I gene and mitochondrial 16S were analyzed to validate the taxonomic classification of M. olmonae. After analyzing 1.2 kilobases, M. olmonae was confirmed as a valid taxonomic classification (Manzanilla et al. 2009).